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By James S. Browning

Mica mining in the United States is confined largely to pegmatites and schists in a few well-defined areas. The largest region extends from central Virginia southward through western North and South Carolina, northern Georgia, and east-central Alabama. 1, 2, 3 Whereas in western North Carolina these pegmatite dikes are weathered to only a shallow depth, they are deeply weathered in the Carolina Piedmont and in Georgia and Alabama. Particularly in Georgia and Alabama, mica is found in the decomposed slates and schists adjacent to the pegmatites, and in deeply weathered granites. Most flake mica is obtained as the major marketable product by crushing and milling pegmatites.4 To a lesser extent, mica is produced as a byproduct of feldspars and spodumene.6 Past research by the Bureau of Mines has developed two methods for mica flotation. One method utilizes acid-cationic flotation for recovery of mica." This method requires thorough desliming of the ore with consequent fine mica losses. The other method utilizes an alkaline-anionic-cationic process for recovering fine size mica from pegmatite ores after desliming sufficiently to remove clay materials but not so drastically as to remove the fine mica. 8, 9, 10, 11, 12, 13 The latter process has also been successfully applied to a micaceous schist ore from California.14 This report summarizes the results of these research studies. Both of the flotation processes developed by the Bureau of Mines have been adopted by the mica industry and are being commercially utilized separately and in combination for flotation of mica from weathered pegmatite ores.

Jan 1, 1969

By Cal D. Iles

Decreasing ore grades and increasing labor and material costs have seriously eroded the economic vitality of many mining operations. Coupled with global economic stagnation and recession in the early 1980's, these conditions have forced reevaluation of operating strategies and methodologies with the objective of remaining competitive in a world marketplace. A concept offering large potential benefits is hardrock portable crushing and conveying. Implementation of this system at Duval Corporation's Sierrita open pit copper-molybdenum mine (Figure 1) has significantly reduced mining costs, becoming a major part of Sierrita's cost reduction strategy. Located 48 km south of Tucson, Arizona, the 209 000 t/d property has one portable 60x89 gyratory ore-crusher in operation with tentative plans for two additional units.

Jan 1, 1985

By Mark Colwell

This paper summarizes the results of a research project whose goal was to provide the Australian coal industry with a longwall installation roadway (faceroad) design methodology that could be utilized by suitably qualified colliery personnel. This goal was achieved in 2012 and the design methodology (and software package) is referred to as Analysis and Design of Faceroad Roof Support (ADFRS). The intended benefits to underground operations, in the provision of this information and resource, are a safer and more productive workplace.

By V. O. Tenorio, J. Puell

"Dump design is critical to effective mine planning in large scale open pit mines. Capital and haulage costs are considerable from early stages and through the life-of-mine as these dumps gradually become immense structures. Delivered mining rates, as well as certain spatial and physical constraints, provide a set of parameters of mathematical and economic relationship that creates opportunities for modeling and thus facilitates the measuring and optimization of ultimate dump design by using programming and empirical techniques while achieving economic objectives. This paper presents a methodology to optimize the ultimate dump design by minimizing its total dumping costs. The methodology consists of the formulation of a generalized model based on the relationship of the main dump parameters, followed by the use of linear programming to find the solution that minimizes the haulage total cost, and finally through a series of iterations, modifies the preliminary solution by projecting it to the topography and creating the ultimate dump design. A case study applied to a waste dump exemplifies this methodology. INTRODUCTION Open pit mine operations move large amounts of material on a daily basis from the shovel faces to the appropriate destination points. Hustrulid et al. identified three major destination places where the material receives downstream treatment after its delivery: mill processing, leaching dumps, and waste rock dumps [1]. The corresponding destination is given by a cut-off grade criteria, ore type, and the possibility of obtaining the maximum metal recovery. Dump leaching technologies have developed substantially since 1975 [2], and have enabled mining facilities to beneficiate low grade sulfide and oxide ores. As a consequence, the number of active dumps have increased since then and the entire mine configuration, which is limited in itself, has changed. The proper location, design, and construction of a mine dump must serve the safety, environmental and economic goals of the long-range mine plans. Therefore, an optimized use of the available surface area in the mine is highly desired."

Jan 1, 2018

By T. Rudolph, M. Pawlik, J. Benndorf, X. Yin, J. F. Brune, P. Goerke-Mallet

The long and often undefined period in the post-mining phase challenges geo-monitoring with its various responsibilities, like the detection of environmental changes, ground movements and water management. Modern methods of geo- and environmental monitoring observe numerous aspects using active and passive sensors with multispectral, hyperspectral and microwave sensors, with diverse spatial dimensions and spatiotemporal resolutions from satellites, Unmanned Aerial Vehicles (UAVs), in-situ sensors. Data integration, together with on-site knowledge and experience, provides the basis for comprehensive modeling, which improves the understanding of the environmental changes and their related causes, which is an essential step for public acceptance. In this paper, we aim to give a brief overview of various geo- and environmental monitoring methods.

Mar 2, 2022

By J. P. Rider

The number of extended cut mining systems has increased significantly in coal mines over the last decade, and there is a constant push to extend the face ventilation systems to even greater setback distances. The need to maintain airflow at setback distances of12.2 m (40 ft) and beyond requires that methods for delivering intake air to the face be improved, or alternative ventilation techniques be implemented. The emphasis of this research effort was to examine various techniques to improve the distribution of available air at the mining face in order to reduce face methane levels. A study was conducted comparing the performance of a jet fan, used in conjunction with a machine mounted scrubber, with blowing curtain ventilation in a 27.5 m (90 ft) heading. In addition, a second study was performed on blowing curtain systems examining how scrubber flow, intake air velocity, and curtain setback influence face methane concentrations. Results showed that when the heading advances to a depth of 27.5 m (90 ft) blowing curtain systems were more efficient at diluting face methane levels when compared to a jet fan. Also, increases in scrubber flows and curtain velocity resulted in lower face methane concentrations for blowing curtain systems at 9.2 and 15.2 m (30 and 50 ft) setbacks.

Jan 1, 1997

Operation of a pilot-scale Floatex density separator was studied using a pyrite concentrate slurry feed. Experimental measurements were further utilized in parameterization of a hindered settling simulation model. The model incorporates particle slip velocity calculation and also a separation efficiency function, adjusted to describe the feed material characteristics. The model was used to compute the overflow and underflow compositions when both fluidization bed pressure and teeter water flow rates were varied. In addition, prediction accuracy and the model validity were evaluated. The simulations gave good results when the teeter interstitial velocities were moderate enough to avoid excessive turbulence in the fluidization. Prediction of the cumulative overflow and underflow size distributions in most experiments yielded essentially less than 10% relative error between the sample data and the estimated value of the 50% passing sizes.

Jan 1, 2011

This paper addresses the valuation and development timing of an undeveloped mineral project. Traditional analysis has us developing the project immediately if its net present value (NPV) is positive. Option pricing theory finds that it is better to wait until the NPV of the property is significantly greater than zero before developing. Alternatively, when evaluating the development timing decision, we must calculate NPV using a higher "timing-adjusted" discount rate, and develop the property only if its NPV using this timing-adjusted discount rate is greater than zero. This paper uses option pricing ideas to convert this development timing advice into a more concrete and user-friendly decision rule: develop the project when its "development-timing NPV" is positive, this development-timing NPV being calculated using the normal discount rate.

Jan 1, 1997

By Osvaldo A. Bascur, J. P. Kennedy

Companies have installed powerful desktops for their personnel and instrumentation and control systems in their plants. These desktops are, in many cases, connected to a company intranet. Still, process engineers have to obtain their data manually. Engineers use process calculations from manually calculated averages from the plant; field operators collect equipment data on log sheets; and maintenance engineers collect critical information on log sheets. All of this information resides in individual machines. What are the strategic tools that will enable collaboration between them? How can operators, engineers, and managers access plant information to proactively increase their effectiveness in process troubleshooting, plant debottleneclung, aligning with business strategic and customer demand, satisfying environmental and safety regulations, developing capital projects, and implementing control strategies? A nonintrusive environment at the desktop is required to provide the process information to these workers. How can value be added to MS Windows technologies with the legacy systems at a minimum cost? There is no straight answer; however, there is a proven framework to leverage the large investments in new technologies. Objects and components are changing the way everyone relates to their computer and networks. Three examples will be described to demonstrate paradigm change. Today, process engineers can access data at the required level of detail for analysis of critical process variables at their desk or remotely. 1. Process Troubleshooting and Analysis: The engineer can develop an inferential calculation, trigger a process advisor to deter- mine the behavior of the units for the last day, and get the population of a set of batches (heats, blocks, rolls, sheets, etc). 2. Process Control and Optimization: The engineer can connect to a process simulator at steady state or a dynamic simulator of the process to evaluate new control strategies or process unit line-ups and use the process simulator as a process observer for fault diagnosis. 3. Collaboration with Accounting and Maintenance: The engineer can review reconciled data and the process mass balances, suggest maintenance cleaning or recalibration of flowmeters, and evaluate key control performance of all advanced controls.

Jan 1, 1999

By D. Naden

Sulphuric acid leaching is the most common method of recovering uranium from its ores and in the following discussion various alternative low cost routes are investigated for recovering uranium from milled ore acid leach liquors. Historically uranium has been recovered from dilute impure leach liquors by packed bed ion exchange (IX), solvent extraction (SX) or a combination of both. All three process routes as commonly practised require complete separation of leached solids and liquids, as well as extensive solids washing in order to reduce soluble uranium losses to a minimum. Separation and washing are costly and often require equipment covering large areas of land. The size and capital cost of the post leach solids washing operation is controlled by the ease of washing the slimes fraction of the ore and the key to the problem of cost reduction, as many others have realised, lies in the ability to separate the slimes fraction of the ore from the more easily washed sands, to wash the sands in low cost equipment and to recover uranium from the slimes stream. Sands and slimes are usually defined in this context as the material larger than, and smaller than, 325 mesh (44 microns). The proposed flowsheets which minimise solid-liquid separation and washing have usually incorporated ion exchange (Refs 1,2,3), and resin in pulp is in fact practised in several mills in the USA (Ref 1). The resins used in these flowsheets and [cranium] recovery throughout the world have been strong base resins which load rapidly and are moderately selective for the uranyl sulphate complex anion over the range of pH which is conveniently achieved in an acid leach operation. Strong base resins are, however, not as selective as weak base resins and weak base liquid reagents owing to the adsorption of competing anions, some of which find their way into the product while others act as resins poisons. Ion exchange using strong base resins must therefore be followed by a more selective weak base SX purification step if pure yellow cake is required.

Jan 1, 1976

By M. Wason

An Ore bed magnetic liner element is made of permanent ceramic magnets embedded in a rubber molding. (See figure 1) They are difficult and expensive to manufacture correctly. Therefore, the lining for a complete mill is expensive, as high as 400% more than conventional rubber liners. The magnets are not very resistant to impact as they are very brittle. Mills of 12 feet or more can use only I inch balls; mills under 12 feet can use balls of 1-1/2 inches. These liners are therefore used in regrind applications with small balls or in secondary pebble mills. Rubber liners for these applications last a long time, so if life was the only consideration, the pay back for these liners would be longer than the life of the mine. The Ore bed liner and its bed of ball chips or magnetic ore is relatively thin and the surface of this bed has a high coefficient of friction. The liners are made so that opposing poles are situated next to each other and that the mill shell and the bed of ore or ball chips completes the magnetic circuit. (See figure 2) The combinations of these properties results in a very efficient liner. Due to the low profile of this bed, there is no material that is lifted too high, so we have a very compact charge with very high attrition, good for fine grinding. These liners have shown a 10% ball consumption reduction and a 10% lower power draw for the same capacity. Due to the magnetic orientation, the bed is formed in a wave shape along the lines of magnetic force. Tests conducted at a copper mine in the southwest United States have confirmed these findings. The mills where the liners were tested are 10.5 feet by 16 feet Hardinge regrind mills operating as overflow ball mills.

Jan 1, 1999

By F. M. Benavides

This paper presents recent developments in federal environmental regulations, which in the view of the author, affect mining and the mineral processing industries. This is a summary of activities by the administration, congress and regulatory agencies during 1990. The information presented is a recap from material published. The emphasis is given to Air Quality regulations, although other environmental concerns are reviewed.

Jan 1, 1991

By Da-Rong Chou

An optimum method for selecting exploratory drilling locations has been developed. The process has been modelled as a highly non-linear programming problem subject to constraints. Solution involves an iterative algorithm which converges rapidly and procedures have been developed to distinguish between local and global optima. The algorithm has been implemented as an interactive computer program which allows the user to influence directly the solution process and to evaluate the effect of any manual adjustments to the optimal solution.

Jan 1, 1984

By W. A. McKinney

In conventional dump leaching of porphyry mine strip wastes, many years are required to extract up to 20 percent of the copper from the contained sulfide minerals. Furthermore, none of the molybdenum, gold, or silver in the strip wastes is recovered by current leaching practices. Because mineralization occurs predominately along fracture planes, breaking of the rock during mining operations liberates and concentrates some of the metal values in the fines. Research shows that upgraded fines can be screened from mine wastes and froth floated for early recovery of copper, molybdenum, gold, and silver. For example, screening a dump sample assaying 0.35 percent copper as chalcopyrite removed about 20 percent of the copper as minus 1/4-inch material that analyzed 0.6 percent copper. About 35 percent of the molybdenum and 20 percent of the gold and silver also reported in the fines. Crushing the mine dump sample to minus 3 inch before screening increased the distribution of copper and molybdenum in the minus 1/4-inch screen fraction to 28 and 50 percent, respectively. Similar results were obtained by screening fines from two other large samples of mine waste dump materials. Flotation studies established that the enriched minus 1/4-inch fines from the three dump samples could be effectively concentrated. Comparative testing revealed that the combination of froth flotation of fines and acid-ferric sulfate leaching of the coarser fraction enabled doubling the recovery of copper over direct leaching of the samples. In addition, significant amounts of molybdenum, gold, arid silver were recovered by flotation.

Jan 1, 1970

By R. N. Edwards

The Magnetometsic Resistivity (MMR) method is based on the measurement of the low-level, low-frequency magnetic fields associated with non-inductive current flow in the earth. The traditional resistivity method maps the electrical properties of the earth by measuring the electric field caused by galvanic current flow between a pair of current electrodes. The MMR method differs from it in that the potential electrodes are replaced by a sensitive coil or magnetometer and a component of the magnetic field due to the current flow is recorded. The presence of an inhomogeneity redistributes the current flow which results in a perturbation of the electric field and, usually, of the magnetic field. The electric field immediately above a relatively conductive inhomogeneity must, by Ohm's Law, be smaller than that expected for a uniform earth. The current density in this region is also reduced but the current density within the inhomogeneity itself is enhanced so that the horizontal component of the magnetic field measured above the inhomogeneity is usually larger than that expected for a uniform earth. A method of interpretation using the magnetic anomaly was patented by Jakoskyl in 1933 but it met with little success at that time. Part of the problem was undoubtedly with the instrumentation, and only recently have robust instruments of sufficient sensitivity been developed2 and field data of good quality obtained. There are many common configurations of the potential and current electrodes in the resistivity method. Similarly, in the MMR method one or both current electrodes may be moved with the magnetometer, either horizontally or vertically ( in a bore-hole), or the current electrodes may be maintained in fixed positions and the magnetometer alone moved. The MMR anomaly is defined as the difference between the

Jan 1, 1975

By David W. Wisecarver

The U.S. Bureau of Mines, in cooperation with U.S. Borax and Chemical Corporation and the Kennecott Copper Corporation, has investigated the use of the microseismic method to evaluate the stability of large, open-pit slope walls. The method is based on the phenomenon that stressed rock normally emits subaudible rock noises, and the number of rock noises per unit time (noise rate) and the magnitude of the rock noises (amplitude) increase as the stresses in the rock approach the failure stress of the rock. Therefore, the detection and recording of those rock noises serve as a semiquantitative method of predicting the incipient failure of rock. This report briefly describes the three different types of microseismic apparatus, the procedures, and the results of microseismic investigations in the slope walls of the Boron Mine near Boron, California, and the Rimbley, Liberty, and Tripp-Veteran open-pit mines near Ely, Nevada. Microsesimic noise rates in stable inactive mining areas are between 0 and 10 noises/ hour; the rates in stable active mining areas are between 10 and 50 noises/hour; and the rate in unstable areas is as high as 2500 noises/ hour. High microseismic noise rates in the Liberty Pit correlate with the time of nearby earthquakes, indicating that the earthquakes affected the slope wall. The results provide evidence that the microseismic tech¬nique is applicable to large pit walls, and that the wide band, wide range microseismic equipment appears to be suitable for open-pit investigations.

Jan 1, 1969

By Michel Dagbert

With the growing demand for energy, explora¬tion for uranium deposits has dramatically increased in the past few years. Since the early ages of uranium exploration, natural gamma ray logs has proved fast and convenient in locating and evaluating mineralized bodies. However, natural gamma ray logging is an indirect measure of the uranium content and in some circonstances, the radiometric signal can be 'altered in a very significant way. To check the presence of any distortion, statistical comparision of radiometric counts and chemical assay values for the same samples is generally performed. Of course in such studies, one inevitably mixes samples where the radiometric signal is really proportional to the uranium content and samples where this signal is influenced by many other sources or distorted before being recorded. Nevertheless, the average tendency leads to correction factors which are then applied to every radiometric reading in the deposit or portion of the deposit where the statistical comparison is made. To account for the "average" character of these correction factors, a parameter of uncertainty like a standard deviation of possible errors is associated to each corrected value. This parameter can be latter used in an ore reserve estimation when the weights assigned to samples should depend on the precision of their grade. The purpose of this paper is to present a new regression technique which can be used without any restrictive hypothesis like a normal or lognormal distribution. Different standard ways which can be used to statistically compare radiometric and chemical assay values for the same sample and to derive a correction factor for the latter will first be reviewed, after a general discussion of disequilibrium problems. The discussion and the examples will be restricted to the case of natural gamma ray logging in drill holes but the methods presented in this paper can also be applied to data from the radiometric probing of a working face or a truck load in an operating mine.

Jan 1, 1979

By J. S. Hall

The productivity and fuel efficiency of iron-ore blast furnace operations has greatly increased in recent times. These improvements, particularly to the Japanese steel industry, have primarily arisen from process engineering studies of the blast furnace and associated operations such as sintering. The development of fluxed sinter based on iron-ore fines reacted to produce highly reducible, low slag sinters has contributed further to a reduction in fuel requirements. The Pilbara province of Western Australia is a significant source of these iron-ore fines supplied to the international market. Increasingly, this market is being offered high quality ores from other foreign sources. To technically assist companies in improving the processing efficiency of ores, and to improve the technical marketing of ores by modelling the processing characteristics of Australian/international ore blends, the Commonwealth Scientific and Industrial Research Organization (CSIRO) is actively assisting the industry by researching the general theme of 'iron ore from mine to metal in this paper we outline progress towards a numerical description of: a. ore deposit classification. b. Degradation during transport. c. Direct reduction of iron ore. d. Liquid bath ore reduction/smelting. e. Industrial sintering.

Jan 1, 1986

By S. E. Phifer

The Haile Gold Mine was the largest gold producer east of the Mississippi River prior to 1942. It is currently the only producing gold mine in the Southeastern United States. Current development involves the mining and heap leaching of some 1000 TPD. Carbon is employed as a recovery medium. Due to its clayey nature and excessive fines in the oxide ore, agglomeration using Portland cement is required prior to leaching. The ore ranges in screen size from two inches to -200 mesh. The agglomerating step combined with certain other conditions has enabled Piedmont Mining Company to achieve recoveries of 90%.

Jan 1, 1987

By Ernest E. Thurlow

"Western Coal" in this paper is limited to those deposits of subbituminous coal and lignite in the States of Montana, Wyoming, and North Dakota. The characteristics of the coal are discussed as well as the history of mining and current mining operations for steam coal. The future of the region is tied closely to the ultimate conversion of coal to oil and gas products. Problems of industrial water supply and environmental considerations are covered together with a brief review of current legislation's actions affecting strip mining.

Jan 1, 1973